Compressor valves come in a variety of designs and are powered open by differential pressure and in the typical known design use some type of a spring to push the valve to the close position. The main issue with such designs is spring fatigue and failure after a predetermined number of cycles. Thus the problem addressed by the present invention is to present a valve design that can provide an economical construction and a reliably long service life. That objective is accomplished by elimination of the spring and the use of a force that preferably has a longer life cycle by using components that are less affected or better withstand the cycling that is the duty of a valve particularly one in a compressor application. In a preferred embodiment, the closing force is provided by the alignment of like poles of permanent magnets. Other embodiments are contemplated that deliver a closing force through a device that is not prone to fatigue or wear as would be experienced in an application involving a spring.
In many applications outside of compressor valves not only have springs been used but they have been combined with electromagnets to create an opening force against a spring return. Hydraulic pistons can also be used in conjunction with springs. These variations are all suggested in related U.S. Pat. Nos. 4,799,507 and 4,869,289. Other examples of electromagnets or permanent magnets for solenoid valves and valve actuators and other applications are U.S. Pat. Nos. 6,179,268; 6,532,919; and 5,356,211. U.S. Pat. No. 6,799,746 relies on a spring inside the valve to return an actuating piston to an original position in response to movement induced by an electromagnet. In yet other applications, such as a door closer in U.S. Pat. No. 4,670,939 a magnet moves a ball that acts as a valve member to control the flow of hydraulic fluid when controlling the closing and opening of a door. U.S. Pat. No. 5,366,506 shows an intraurethral valve with a magnetic valve member that can be selectively opened to allow urine to pass by moving another magnet from outside the body. The following patents show the general state of the art of compressor valves: U.S. Pat. Nos. 6,810,901; 6,790,018; 6,751,941; 6,684,651; 6,644,945; 6,585,500; 6,152,710; 5,947,708; 5,885,062; 5,547,344; 5,025,828; 4,793,779 and 4,446,608.
What is needed, particularly in a compressor application where a reciprocating compressor that runs at 300-1800 RPM and has valves that cycle between 5-20 times per second corresponding to that speed is a more reliable closing force that improves on the service life seen from coil springs or plate type closing springs. While the preferred embodiment is to use neodymium-iron-boron permanent magnets with similar poles facing, those skilled in the art will appreciate the full scope of the invention from the specification and claims, which appear below.